After the removal of KindleGen and the replacement of it with Kindle Previewer, resulting in changes to Papyrus Author to support this, Amazon seem to be now recommending that we use ePub files to upload.
I got an update to Kindle Previewer the other day and every time I create and preview a Mobi file it now shows me this popup:
So, it looks like we don’t need .mobi any more, doesn’t it?
At the very least, .mobi files are incredibly useful if you want to distribute/load ebooks reliably directly to Kindle readers.
We’ll follow how this recommendation pans out technically, but I believe this is partly because they used to recommend submitting .doc and .rtf files in the past. That was owed to too many badly formatted ebooks being submitted - KDP hopes to get a file that went through as few conversions as possible.
You should always check the results, but both our .mobi and .epub should come out fine after submitting to KDP.